Theoretical assessment of irradiation swelling in beryllium

• Published in: Journal of nuclear materials 1996-10, Vol.233 (1-3), p.832-836
• Main Authors: Dubinko, V.I., Barabash, V.R.
• Format: Article
• Language: English
• ISSN: 0022-3115; 1873-4820
• DOI: 10.1016/S0022-3115(96)00288-7

Current models of irradiation swelling in beryllium are based on the assumption that the swelling arises from bubble growth rather than void growth. However, the factors governing cavity formation in beryllium are more complex than those in cubic metals which are based on elastic interaction difference (EID) between vacancies and self-interstitial atoms. Beryllium belongs to the set of hexagonal close-packed metals where diffusion has been shown to be anisotropic. Diffusional anisotropy difference (DAD) between point defects changes the cavity bias for their absorption and leads to dependence of the dislocation bias on the distribution of dislocations over crystallographic directions. This results in new critical quantities for the bubble—void transition that controls transition from low-dose to high-dose irradiation effects. In the present paper, we show how the critical parameters controlling irradiation swelling in beryllium depend on the distribution of dislocations over crystallographic directions taking into account an anomalously high anisotropy of self-diffusion in beryllium. The latter is shown to be in agreement with experimentally observed resistance of beryllium to void swelling at early stages of irradiation when a-type dislocations prevail over c-type dislocations. However, a mechanism of radiation-induced production of c-type dislocation loops is proposed that can lead to a subsequent transition of bubbles to voids.